1. Field of the Invention
This invention relates to packed tower aerators. More particularly, the present invention relates to packed tower aerators that are staged to improve decontamination efficiency and minimize outlet air.
2. Description of the Background Art
Hydrogen sulfide is a common water contaminant that is easily identified by its rotten egg order. It is most commonly the result of sulfur bacteria that uses natural sulfur compounds as a food source. Hydrogen sulfide contamination is typically found in water with low levels of dissolved oxygen and pH level of less than 6.5. Although it is an impurity, it does not pose a healthy risk at the levels most commonly found in driking water. Nonetheless, hydrogen sulfide gives water a noxious order and objectionable taste.
Currently, there exists a variety of methods to remove hydrogen sulfide contamination from water. These methods include chemical treatments, filtration techniques and aeration. Aeration involves the “stripping” of hydrogen sulfide by forcing a volume of air through the contaminated water. The stripping is achieved within a volume of mass transfer media that facilitates water-air interaction. The forced air dissolves the hydrogen sulfide within the water and removes the contamination as a volatile gas. The contaminant laden air must thereafter be collected and treated to control odors, as local government agencies often regulate the purity of air discharged to the environment.
The background art contains numerous examples devices for stripping contaminants from water. For instance, U.S. Pat. No. 5,378,267 to Bros et. al. discloses a modular air stripping apparatus. The apparatus includes a stacked series of intermediate stripping chambers for use in removing volatile organic compounds from water. Air flows upwardly through the chambers wherein it flows through water passing over the floors of the chambers.
U.S. Pat. No. 5,876,662 to Jain discloses an odor control system for removing hydrogen sulfide from a gas stream. The system employs a boxlike housing that contains three sequentially connected treatment chambers. The treatment chambers each contain a suitable packing wherein chemical reactions occur based on mass transport principles.
Another hydrogen sulfide removal apparatus is disclosed in U.S. Pat. No. 6,080,306 to Falkner. The apparatus of Falkner discloses an apparatus that causes sufficient oxygen to be dissolved in water for a sufficient amount of time and at a sufficient pressure such that solid elemental sulfur is precipitated.
Finally, U.S. Pat. No. 6,773,582 to Anthony discloses a drinking water treatment system that includes hydrogen sulfide scrubbers for treating hydrogen sulfide gas flow from an aerator. The scrubbers employ scrubbing solutions that include a triazine compound.
Although each of the above referenced inventions achieves its individual objective, they all suffer from common problems. For instance, prior aerators require large volumes of mass transfer media in order to adequately clean contaminants from the water supply. In the case of hydrogen sulfide contaminants, the volume of media necessary to achieve suitable purity must be housed in an aeration tower at least 10 to 14 feet high. This results in towers that are unsightly, difficult to service, and expensive.
Additionally, prior aeration systems all require elaborate odor control systems for the outlet air. These odor control systems are often mandated by governmental agencies to prevent the escape of noxious smelling orders. The requirement of odor control systems for packed aeration towers adds greatly to the cost of such towers.
Thus, there exists a need in the art for a packed tower aerator that removes contaminants in a more efficient manner, thereby reducing the volume of mass transfer media needed and the size of the tower housing such media. There further exists a need in the art for a packed tower aerator that reutilizes the outlet air thereby minimizing the size of odor control systems.